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The Structures of DNA and RNA Genome s DNA Replication DNA Repair and Recombination

Introduction to Molecular Genetics. The Structures of DNA and RNA Genome s DNA Replication DNA Repair and Recombination Transcription and Processing Translation Control of Gene Expression Manipulating DNA and RNA.

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The Structures of DNA and RNA Genome s DNA Replication DNA Repair and Recombination

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  1. Introduction to Molecular Genetics • The Structures of DNA and RNA • Genomes • DNA Replication • DNA Repair and Recombination • Transcription and Processing • Translation • Control of Gene Expression • Manipulating DNA and RNA http://priede.bf.lu.lv/ Studiju materiāli / MolekularasBiologijas / Ievads MolGen / EN

  2. DNA replication Molecular Biology of the Gene, 5th Edition

  3. The replication of DNA is a complex, multi-step process, involving many enzymes

  4. Nucleotide sequence of a DNA strand (the template strand) is copied through complementary base pairing into complementary sequence DNA synthesis is TEMPLATED

  5. Molecular Biology of the Gene, 5th Edition DNA polymerase (enzyme that does the work) needs a single-stranded template, primer and dNTPs

  6. DNA is always synthesized in the 5’-to-3’ direction Molecular Biology of the Gene, 5th Edition

  7. DNA polymerase resembles a hand that grips primer-template junction

  8. DNA polymerase ‘monitors’ ability of the incoming nucleotide to base-pair with the template nucleotide Molecular Biology of the Gene, 5th Edition

  9. Molecular Biology of the Gene, 5th Edition Yet, a wrong base is occasionally added (when it is in an unusual tautomeric form)

  10. EXONUCLEOLYTIC PROOFREADING by DNA polymerase corrects most of these errors template primer Please, be so kind and find an error in this figure!

  11. EXONUCLEOLYTIC PROOFREADING by DNA polymerase corrects most of these errors

  12. DNA replication is SEMICONSERVATIVE • Each strand of parental DNA serves as a template for a new, complementary strand • The 2 new double helixes each have 1 parental strand and 1 newly synthesized strand

  13. Life The Science of Biology, 7th Edition Should it necessarily be so?

  14. Meselson and Stahl (1958) proved that replication is semiconservative

  15. Both strands are synthesized together at the REPLICATION FORK Lewin, Genes

  16. There is a problem with the simplest model direction of strand growth direction of replication direction of strand growth

  17. The replication fork is ASYMETRIC:one strand (leading) grows continuously, while the other (lagging) is synthesized as fragments

  18. Molecular Biology of the Gene, 5th Edition Two DNA polymerases operate at the replication fork

  19. DNA polymerase needs a primer:primer (RNA!) is provided by DNA primase

  20. Lagging strand is synthesized stepwise (RNAse H)

  21. DNA ligase uses ATP to seal the nicks between fragments (ligation reaction)

  22. Sliding clamp helps DNA polymerase not to fall off the template Molecular Biology of the Gene, 5th Edition

  23. Molecular Biology of the Gene, 5th Edition DNA polymerase needs a single-stranded DNA template: DNA helicase ‘opens’ the parental double helix

  24. DNA polymerase needs a single-stranded DNA template:SSB proteins stabilize the unwound strands

  25. The ‘winding’ problem Lehninger. Principles of Biochemistry, 3rd Edition

  26. Topoisomerases remove positive supercoils Molecular Biology of the Gene, 6th Edition

  27. The major types of proteins at a bacterial replication fork

  28. The proteins involved in replication are arranged in a complex

  29. Replication is initiated at the origins (ori) of replication

  30. Mechanism of initiation in bacteria

  31. Bacterial chromosomes are replicated from single origin

  32. Eukaryotic chromosomes are replicated from many origins Molecular Biology of the Gene, 5th Edition

  33. Molecular Biology of the Gene, 5th Edition Eukaryotic chromosomes have redundancy of ori;all origins are inactivated by DNA replication

  34. New nucleosomes are assembled right behind the replication fork

  35. Patterns of histone modification can be faithfully inherited

  36. Inheritance of chromatin structures is a mechanism of the EPIGENETIC INHERITANCE

  37. The End Replication Problem Molecular Biology of the Gene, 6th Edition

  38. Solving the end replication problem: TELOMERES & TELOMERASE Molecular Biology of the Gene, 5th Edition

  39. Bacterial chromosomes have no ends & hence no end replication problem Molecular Biology of the Gene, 5th Edition

  40. Single-stranded genomes (viruses) replicate through synthesis of complementary strands

  41. Why is the genetic information stored in form of double-stranded DNA in all cells?

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